1. Field of the Invention
The present invention relates to filters for filtering liquids, such as water. More particularly, the present invention relates to a collapsible filter that may be collapsed to reduce its volume for storage and expanded to increase its volume for use.
2. Description of the Prior Art
Filters of various configurations for filtering gasses and liquids are employed daily in households. These filters are used to remove chemical impurities as well as remove and hold particulate matter from passing along with the filtrate.
The making of a pot of coffee is one example of a household use of filters. Most coffee drinkers will generally agree that coffee tastes better when it is made with water that has been filtered to adsorb impurities, especially chemical impurities, that affect flavor. For example, heavily chlorinated water, typically found in tap water obtained from municipal water supplies, or water having a high calcium content, can detract from the flavor of coffee.
In most households, coffee is typically made in a drip type coffee maker. Such coffee makers have a pot seated on a heating element. The pot is positioned below a brew basket. The brew basket supports a fluted or pleated bowl shaped paper coffee filter element in which coffee grounds are placed. The paper coffee filter element held in the brew basket generally does not filter chemical impurities, but rather, only relatively large particulates such as the coffee grounds. Heated water is delivered into the brew basket by a water outlet connected to a water tank through a thermo siphon. The heated water drops onto and contacts the coffee grounds held by the paper coffee filter. The extracted coffee passes through the paper filter into the coffee pot below. The coffee in the pot is kept warm by the heating element.
The typical brew baskets found in most coffee makers have an inverted frustaconical shape. The paper filter element generally conforms to the inverted frustaconical shape of the brew basket. Generally, after each pot of coffee, the paper coffee filter in the brew basket must be replaced with a fresh paper filter. Typically, such paper filter elements are sold in packaging comprising nested lots of 25 to 50 filter elements.
As discussed above, such paper filter elements are not designed to remove impurities, and therefore, they do not substantially improve the taste of coffee. Rather, the principal function of such filters is to support the coffee grounds and prevent the grounds from passing into the coffee in the underlying coffee pot. Thus, another filter must be employed to remove impurities from the water before the water contacts the coffee grounds.
Accordingly, it is desirable to have a filter that is conveniently useable with a drip type coffee maker to filter impurities from the water prior to the water contacting the coffee grounds. It is also desirable to provide a filter whose volume may be minimized for storage and commercial packaging purposes but expanded to a sufficient volume to provide an adequate fluid reservoir during use of the filter. It is also desirable to provide a filter that efficiently removes impurities with a low resistance to flow so that the impurities may be filtered out of the water without increasing the time required to brew a pot of coffee. It is further desirable to provide such a filter that can be supported within the brew basket of a typical drip type coffee maker.